Stringent evaporative emission test standards for internal combustion engines have been implemented by various governmental agencies to reduce fuel vapors released from a vehicle's fuel delivery system into the surrounding environment.
Some fuel vapor control systems may include an evaporation canister configured to capture fuel vapors during refueling events in the vehicle. US 2006/0053868 provides a fuel vapor control system configured to spin the vehicle's internal combustion engine to draw down the manifold air pressure (MAP) and create a vacuum within the intake manifold. Fluidic communication between the fuel vapor emission control system and the intake manifold is permitted after the MAP has been drawn down. Then a diagnostic test is performed to determine the fuel vapor control system's integrity once the pressure within the fuel vapor control system has been decreased.
However, the Applicants have recognized several problems with the above fuel vapor control system. For example, spinning the engine to perform a diagnostic test may decrease operating efficiency of the vehicle as well as cause unnecessary wear on various engine components, such as the electric motor used to spin the engine as well as the cylinder valves. Moreover, the diagnostic test described above determines the integrity of the entire fuel vapor control system, preventing separate components from being diagnosed.
As such in one approach, a method for operating a fuel vapor control system included in a vehicle having an engine is provided. The method including storing positive or negative pressure in fuel tank while isolated from an evaporation canister region, transferring at least a portion of the stored pressure to the canister region and indicating degradation of the evaporation canister region based on a response of the transferred pressure in the canister region while the canister region is isolated from the fuel tank.
In this way, it is possible to utilize pressure that may be passively generated in one portion of the system, even during shut-down engine operation, to verify the integrity of another portion of the system. Further, it is possible to verify the integrity of different portions of the system. Thus, it can be possible to more completely test the system, as well as increase the number of evaporation canister testing events. Such a method may be particularly beneficial for use in a plug-in hybrid vehicle due to the fact that the internal combustion engine may not be operated for an extended duration of time. However, it will be appreciated that the aforementioned method may be applied to other types of vehicles utilizing internal combustion engines.
It should be understood that the background and summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.